D-Glucose 6-phosphate (G6P) is glucose that hydroxyl group on carbon 6 is phosphorylated by hexose kinase and is involved in glycolysis, gluconeogenesis, and the pentose phosphate pathway, as well as being converted to glycogen or starch storage. G6P serves as a substrate for glucose 6-phosphatase in the liver and hexose 6-phosphate dehydrogenase (H6PDH) in the lumen of the endoplasmic reticulum.